Specifying a Secondary Master Server

To specify that a server is to be the secondary server for a given zone, you create "secondary" records in that server's named.boot file. Separate records can designate the server as a secondary server for the zone, the zone's reverse address domain, and the loopback host.

A "secondary" record has three required fields:

• The first field designates the server as "secondary."

• The second field identifies the zone it serves.

• The third field identifies the IP address of the primary server for the zone from which the secondary server obtains its authoritative data.

A "secondary" record can have one or more optional fields after the required fields. The optional fields are:

• Secondary servers. After the IP address of the primary server, you can add IP addresses of other secondary servers. These provide additional sources from which the secondary server can obtain data. Adding IP addresses of secondary servers may under some circumstances reduce performance, unless those IP addresses are additional network addresses of a multihome primary server.

• Backup file. After the IP address of the primary (and optional secondary) server(s), you can add the name of a backup hosts file. If a backup file name is present, the secondary server loads its data from that file, then checks with the primary (and optional secondary) servers to make sure that the data in the backup file is up to date. If the backup file is not up to date, it is brought up to date, based on the information received from the primary server.

For example, the following lines in a boot file specify that the server is the secondary server for the doc.com zone and its reverse address domain; that it obtains its authoritative data from the primary server with an IP address of 129.146.168.119, that it uses the server 192.146.168.38 as a secondary source of zone data, and initially loads its data from the file doc.com.bakup:

 
secondary   doc.com   129.146.168.119  192.146.168.38  doc.com.bakup
secondary   4.0.32.128.in-addr.arpa       129.146.168.119 

In the context of the various example files presented in this chapter, the sample boot file lines above correspond to the boot file of the dnssecondary server, which is an alias for the sirius machine whose IP address is 192.146.168.38.

A server can act as the primary server for one or more zones, and as the secondary server for one or more zones. The mixture of entries in the boot file determines whether a server is a primary or secondary server for a given zone